1. Field of the Invention
This invention relates to blends of olefin polymers and ethylene vinyl-alcohol copolymers, and, more particularly, to films and other products that contain these blends.
2. Discussion of the Art
Ethylene-vinyl alcohol copolymers are frequently used in multilayer film constructions with olefin polymers because, together, these polymers provide excellent resistance to permeation by oxygen, water, and hydrocarbons. Blends of ethylene-vinyl alcohol copolymers and olefin polymers provide excellent barrier properties when the ethylene-vinyl alcohol copolymer is distributed in thin, ribbon-like overlapping layers that may or may not be the continuous phase. See, for example, U.S. Pat. No. 4,971,864.
Several investigators have studied blends containing ethylene-vinyl alcohol copolymers and olefin polymers. Such studies have been limited to the effects of using high modulus resins having ethylene copolymer concentrations below 38%. It has not been possible to make superior barrier films from materials having lower modulus values and higher ethylene copolymer ratios.
Many multilayer products available today contain so-called scrap layers, which consist of blends of ethylene-vinyl alcohol copolymer and olefin polymers. Because of processing conditions conventionally used to treat scrap material, films formed from these blends have not been found to be particularly useful as barrier layers. Scrap material is generally used as a filler in films. It would be desirable to develop a fine laminar structure in a layer of scrap material, thereby improving performance of the material as a barrier layer without significantly increasing cost. Additionally, applications requiring flexibility are often difficult to provide and require excessive barrier material because of the stiffness and attendant cracking of the barrier material. Thus, it would be desirable to provide a blend of low modulus copolymer(s) of ethylene-vinyl alcohol and olefin polymer(s) that could be successfully used in barrier materials.